From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D54FFC433ED for ; Fri, 30 Apr 2021 05:59:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B29A26147D for ; Fri, 30 Apr 2021 05:59:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230310AbhD3F74 (ORCPT ); Fri, 30 Apr 2021 01:59:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:53150 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230045AbhD3F7z (ORCPT ); Fri, 30 Apr 2021 01:59:55 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id E59C3613A9; Fri, 30 Apr 2021 05:59:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1619762348; bh=1CKbKM0R4kK3bXyDGvN1pK7hcVHzG+6Ji14Gb37yn9g=; h=Date:From:To:Subject:In-Reply-To:From; b=V+p7+38reEfbhf/rTyETFeNLLiKRWxwb+Qp9j4+9vdou7EAavt0sNOI5mLY1asdPN /Y/mFqbHb+/vCT5NCB8hEIGqO/m2phGLiHXgRDrKa5UNJU+6M3ZXJQlNDbhySlRwv+ 5UQyiPCOI4k6O+Zk3EJ9fLR291l4dA8LbT4ESmzA= Date: Thu, 29 Apr 2021 22:59:07 -0700 From: Andrew Morton To: akpm@linux-foundation.org, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, urezki@gmail.com, vjitta@codeaurora.org Subject: [patch 115/178] mm: vmalloc: prevent use after free in _vm_unmap_aliases Message-ID: <20210430055907.ycr60LTRb%akpm@linux-foundation.org> In-Reply-To: <20210429225251.02b6386d21b69255b4f6c163@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Vijayanand Jitta Subject: mm: vmalloc: prevent use after free in _vm_unmap_aliases A potential use after free can occur in _vm_unmap_aliases where an already freed vmap_area could be accessed, Consider the following scenario: Process 1 Process 2 __vm_unmap_aliases __vm_unmap_aliases purge_fragmented_blocks_allcpus rcu_read_lock() rcu_read_lock() list_del_rcu(&vb->free_list) list_for_each_entry_rcu(vb .. ) __purge_vmap_area_lazy kmem_cache_free(va) va_start = vb->va->va_start Here Process 1 is in purge path and it does list_del_rcu on vmap_block and later frees the vmap_area, since Process 2 was holding the rcu lock at this time vmap_block will still be present in and Process 2 accesse it and thereby it tries to access vmap_area of that vmap_block which was already freed by Process 1 and this results in use after free. Fix this by adding a check for vb->dirty before accessing vmap_area structure since vb->dirty will be set to VMAP_BBMAP_BITS in purge path checking for this will prevent the use after free. Link: https://lkml.kernel.org/r/1616062105-23263-1-git-send-email-vjitta@codeaurora.org Signed-off-by: Vijayanand Jitta Reviewed-by: Uladzislau Rezki (Sony) Signed-off-by: Andrew Morton --- mm/vmalloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/vmalloc.c~mm-vmalloc-prevent-use-after-free-in-_vm_unmap_aliases +++ a/mm/vmalloc.c @@ -2040,7 +2040,7 @@ static void _vm_unmap_aliases(unsigned l rcu_read_lock(); list_for_each_entry_rcu(vb, &vbq->free, free_list) { spin_lock(&vb->lock); - if (vb->dirty) { + if (vb->dirty && vb->dirty != VMAP_BBMAP_BITS) { unsigned long va_start = vb->va->va_start; unsigned long s, e; _